Associations of Escherichia coli K-12 OmpF trimers with rough and smooth lipopolysaccharides.

The associations of both rough and smooth lipopolysaccharides (LPS) with the OmpF porin of Escherichia coli K-12 were examined in galE strains deleted for ompC. Transformation with pSS37 and growth with galactose conferred the ability to assemble a Shigella dysenteriae O antigen onto the core oligosaccharide of E. coli K-12 LPS. The association of LPS with OmpF trimers was assessed by staining, autoradiography of LPS specifically labeled with [1-14C]galactose, and Western immunoblotting with a monoclonal antibody specific for OmpF trimers. These techniques revealed that the migration distances and multiple banding patterns of OmpF porin trimers in sodium dodecyl sulfate-polyacrylamide gels were dictated by the chemotype of associated LPS. Expression of smooth LPS caused almost all of the trimeric OmpF to run in gels with a slower mobility than trimers from rough strains. The LPS associated with trimers from a smooth strain differed from the bulk-phase LPS by consisting almost exclusively of molecules with O antigen.     

Characterization of cloned alpha-satellite sequence from the extrachromosomal DNA of HeLa cell culture]

We have obtained the alphoid DNA clones, pK1 and pK2, from the extrachromosomal DNA of Hela cells treated by cycloheximide (30 micrograms/ml). Nucleotide sequences of the clones were aligned. The sides of the pK1 and pK2 are 390 and 184 bp, respectively. The marked RELP for the clones was not observed. The results of in situ hybridization have shown an approximately equal distribution of Ag-grains over major part of human chromosomes, with a slight preference for chromosomes 1, 5 and 19 (the 1-st group of alpha-satellite DNA). Therefore, the obtained alphoid sequences seem to be rather conservative and non-chromosome-specific. We suppose that increase of the alphoid DNA content in the fraction of the extrachromosomal DNA under the cycloheximide treatment is a result of the sporadic statistical processes rather then consequence of the specific excision.     

Cyclic AMP efflux is regulated by occupancy of the adenosine receptor in pig aortic smooth muscle cells

Cultured pig aortic smooth muscle cells respond to extracellular adenosine by activating adenylate cyclase and by initiating the efflux of cAMP. In the presence of extracellular adenosine, efflux is first order with respect to intracellular cAMP concentration up to at least 125 pmol/10(6) cells. The apparent first-order rate constant for the efflux of cAMP increases in a dose-dependent manner in response to extracellular adenosine or 5-N-ethylcarboxamide adenosine. The EC50 for adenosine for promoting cAMP efflux is 12 microM. For cells stimulated with 5-N-ethylcarboxamide adenosine, the EC50 is 5 microM. When extracellular adenosine is removed, efflux stops abruptly. Cellular cAMP content falls but is still in a range that supports cAMP efflux when agonist is present. Efflux is not affected by H8 (N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride), an inhibitor of cAMP-dependent protein kinase. These data suggest that in pig aortic smooth muscle cells, the efficiency of cAMP efflux is regulated by A2 receptor occupancy.     

Antiatherogenic action of corn oil in experimental atherosclerosis]

Therapeutic effect of corn oil was studied in rabbits with alimentary atherosclerosis. Corn oil was administered (2 ml/kg, 30 days) after the completion of cholesterol diet unlike studies, where they were administered simultaneously. Total cholesterol, apoB-lipoprotein cholesterol and triglycerides decreased more intensively in rabbits fed by corn oil than in control group. No changes in high-density lipoprotein cholesterol were observed. The most pronounced effect was noted in aorta morphological analysis: an aorta damage degree was 4.8% as compared with 52.9% in the control group. The results show that available plant oils with omega-6 polyunsaturated fatty acids (PUFA), in particular corn oil, may as well as omega-3 PUFA be used as the base for antiatherogenic preparations.     

Characterization of Propionibacterium plasmids

Plasmid DNAs from 15 Propionibacterium strains were characterized by using restriction endonuclease analyses, DNA-DNA hybridizations, and curing experiments. Restriction endonuclease analysis identified seven distinct plasmids (pRGO1 through pRGO7). Detailed restriction maps were constructed for four of these plasmids. DNA-DNA hybridization analysis revealed that plasmids pRGO1 and pRGO2 had extensive sequence homology and that both were homologous to pRGO7 and to similar sequences of pRGO5. Plasmids pRGO4 and pRGO6 did not have any significant sequence homology with any of the other plasmids. Plasmid pRGO3 had partial sequence homology only with pRGO7. Curing of plasmids pRGO1, pRGO2, and pRGO5 was achieved by treatment with acriflavin, but we failed to identify any plasmid-encoded bacteriocin production, carbohydrate fermentation, or antibiotic resistance. However, physical evidence was obtained that tentatively linked the clumping phenotype of Propionibacterium jensenii P38 with plasmid pRGO5.     

Chemical dependency and drug testing in the workplace.

Urine testing for drug use in the workplace is now widespread, with the prevalence of positive drug tests in the work force being 0% to 15%. The prevalence of marijuana use is highest, and this can be reliably tested. Though it is prudent to rid the workplace of drug use, there is little scientific study on the relationship of drug use and workplace outcomes, such as productivity and safety. Probable-cause testing and preemployment testing are the most common applications. Random testing has been less accepted owing to its higher costs, unresolved legal issues, and predictably poor test reliability. Legal issues have focused on the right to policy, discrimination, and the lack of due process. The legal cornerstone of a good program is a policy that is planned and agreed on by both labor and management, which serves both as a contract and as a procedure in which expectations and consequences are known. The National Institute on Drug Abuse is certifying laboratories doing employee drug testing. Testing methods when done correctly are less prone to error than in the past, but screening tests can be defeated by adulterants. Although the incidence of false-positive results is low, such tests are less reliable when the prevalence of drug abuse is also low.     

Dynamic changes of microtubule and actin structures in CV-1 cells during electrofusion

To study the involvement of the cytoskeletal system in the fusion of animal cells, we examined the dynamic changes of cytoskeletal proteins during the various stages of cell fusion. CV-1 cells were fused by applying a radio-frequency electrical pulse. Structural changes of microtubules (MTs) and F-actin were monitored simultaneously by double-label fluorescence microscopy. It was observed that in a few minutes after the initiation of cell fusion, MT bundles began to extend into the cytoplasmic bridges which were formed by fusing the membranes of neighboring cells. Later, a network of parallel MT bundles appeared between the adjacent nuclei of the fusing cells; such MT bundles may provide the mechanical links that are responsible for nuclear aggregation. The structural changes of F-actin during cell fusion were more complicated. We observed many different patterns of actin distribution in the fusing cells, including some giant, ring-shaped structures. Reorganization of actin is unlikely to be involved in the nuclear aggregation process. Instead, actin bundles condensed at the cell edges may help to widen the cytoplasmic bridges to allow merging of cellular contents between the fusing cells.     

Effects of spaceflight on the proliferation of jejunal mucosal cells

The mitotic indices, villus heights, and crypt depths were determined in each of three jejunal regions (proximal, middle, and distal) for five animals each in the flight, vivarium, and synchronous groups. Because of the rapid turnover of intestinal mucosal cells and the delay in recovering the flight animals, it is not known whether the proliferation of jejunal mucosal cells is affected by microgravity conditions associated with spaceflight. However, since there were no consistent differences between animals in the flight group and those in the synchronous and vivarium control groups, it appears that any effects of microgravity on the turnover of jejunal mucosal cells are short-lived. Thus, this study represents an initial step in determining the effects of microgravity on the proliferation and turnover of intestinal mucosal cells.     

Zidovudine (azido dideoxythymidine) inhibits characteristic early alterations of lymphoid cell populations in retrovirus-induced murine AIDS

Using flow cytometry technology and multiparameter analyses, we report early and characteristic alterations in lymphoid cell profile in spleen and lymph nodes due to LP-BM5 retrovirus disease (murine AIDS (MAIDS)) and the effect of azido dideoxythymidine, a nucleoside inhibitor, on these changes. MAIDS has been characterized by rapid and profound lymphoproliferation accompanied by hypergammaglobulinemia and immunosuppression. As early as 2 wk postinfection, there is a selective depletion of CD8+ cells whereas the total number of CD4+ cells increases throughout the first 8 wk of infection although the frequency is relatively stable. These population changes were partially delayed by oral AZT therapy for 6 wk postinfection. Ly-6C (AL-21) is expressed on roughly 50% of CD4+ and CD8+ cells in C57BL/6 mice. In MAIDS, the residual population of CD8+ cells is primarily Ly-6C+. The CD4+ cells have a transient increase in ratio of Ly-6C+/Ly-6C- cells at 2 wk postinfection but by 6 wk are primarily Ly-6C-. There was an increase in both the total number and percentage of Mac 1+ cells and a selective depletion of certain splenic B cell subpopulations. Azido dideoxythymidine delays these early population changes.